package org.apache.maven.project;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.codehaus.plexus.classworlds.realm.ClassRealm;
import org.codehaus.plexus.component.annotations.Component;
import org.eclipse.aether.graph.DependencyFilter;

/**
 * Default project realm cache implementation. Assumes cached data does not change.
 */
@Component(role = ProjectRealmCache.class)
public class DefaultProjectRealmCache implements ProjectRealmCache {

  private static class CacheKey {

    private final List<? extends ClassRealm> extensionRealms;

    private final int hashCode;

    public CacheKey(List<? extends ClassRealm> extensionRealms) {
      this.extensionRealms = (extensionRealms != null) ? extensionRealms : Collections.<ClassRealm> emptyList();

      this.hashCode = this.extensionRealms.hashCode();
    }

    @Override
    public int hashCode() {
      return hashCode;
    }

    @Override
    public boolean equals(Object o) {
      if (o == this) {
        return true;
      }

      if (!(o instanceof CacheKey)) {
        return false;
      }

      CacheKey other = (CacheKey) o;

      return extensionRealms.equals(other.extensionRealms);
    }

  }

  private final Map<CacheKey, CacheRecord> cache = new HashMap<CacheKey, CacheRecord>();

  public CacheRecord get(List<? extends ClassRealm> extensionRealms) {
    return cache.get(new CacheKey(extensionRealms));
  }

  public CacheRecord put(List<? extends ClassRealm> extensionRealms, ClassRealm projectRealm,
      DependencyFilter extensionArtifactFilter) {
    if (projectRealm == null) {
      throw new NullPointerException();
    }

    CacheKey key = new CacheKey(extensionRealms);

    if (cache.containsKey(key)) {
      throw new IllegalStateException("Duplicate project realm for extensions " + extensionRealms);
    }

    CacheRecord record = new CacheRecord(projectRealm, extensionArtifactFilter);

    cache.put(key, record);

    return record;
  }

  public void flush() {
    cache.clear();
  }

  public void register(MavenProject project, CacheRecord record) {
    // default cache does not track record usage
  }

}
